On 2/23/19 4:24 PM, Eric Blake wrote:
Right now, copying the state of a transient domain with snapshots from one host to another requires multiple API calls on both machines - on the host: get the domain XML, get a list of the snapshots, and then for each snapshot get the snapshot's XML; then on the destination: create the domain, then multiple domain snapshot create calls with the REDEFINE flag. This patch aims to make the process use fewer APIs by making it possible to grab the XML for all snapshots at the same time as grabbing the domain XML. Note that we had to do the modification to virDomainGetXMLDesc(), rather than virDomainSnapshotGetXMLDesc(), since the latter requires a single non-NULL snapshot object, whereas we want the list of all snapshots for the domain (even if the list has 0 elements).
Once wired up in drivers in later patches, the new information is provided as:
<domain ...> ... </devices> <snapshots current='name'> <domainsnapshot> ... </domainsnapshot> <domainsnapshot> ... </domainsnapshot> </snapshots> </domain>
For now, I did not modify the schema to permit this information during virDomainDefineXML; it is still necessary to use virDomainSnapshotCreateXML with VIR_DOMAIN_SNAPSHOT_CREATE_REDEFINE multiple times to recreate the added state output here.
Unfortunately, libvirt versions between 1.2.12 and 5.0.0 will silently ignore the new flag, rather than diagnosing that they don't support it; but at least silent lack of snapshots from an older server is not a security hole.
Signed-off-by: Eric Blake <eblake@redhat.com> --- include/libvirt/libvirt-domain.h | 1 + src/conf/domain_conf.c | 13 ++++++++----- src/libvirt-domain.c | 5 +++++ 3 files changed, 14 insertions(+), 5 deletions(-)
[...]
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c index 072b92b717..2691698bd5 100644 --- a/src/libvirt-domain.c +++ b/src/libvirt-domain.c @@ -2570,6 +2570,11 @@ virDomainGetControlInfo(virDomainPtr domain, * XML might not validate against the schema, so it is mainly for * internal use. * + * If @flags contains VIR_DOMAIN_XML_SNAPSHOTS, the XML will include
Should we even try to say that "and supported by the target libvirt system with the appropriate version of the software installed" ;-)... I know implied somewhat - but perhaps notable in this (and future) cases because of the issue mentioned in the commit message that outward facing docs consumers may never read.
+ * an additional <snapshots> child element describing all snapshots + * belonging to the domain, including an attribute current='name' if + * one of those snapshots is current. + * * Returns a 0 terminated UTF-8 encoded XML instance, or NULL in case of error. * the caller must free() the returned value. */
Reviewed-by: John Ferlan <jferlan@redhat.com> John